7. Agent Coulson
This one is
really contentious, isn't it? We all thought Agent Phil Couslon had met his definite, untimely end mid-way through The Avengers when he wound up impaled by Loki. However, the announcement of a S.H.I.E.L.D. TV show that would feature Coulson has caused fans to assume that, in fact, Coulson isn't dead, and the classic movie maxim holds true - if you didn't see them die, they're probably not dead. We saw Coulson bleeding out and surely near death, but we didn't see him definitively expire. Hence, he could make a cursory appearance in Iron Man 3 and clear all this up. Yes, this will be a tricky manoeuver to pull off, and will somewhat cheapen the emotional aspects of The Avengers, but the character is so likeable that we don't
want him to be dead; as long as it was done in a way that engaged with the comics, I wouldn't have a huge problem with it. An easy way for this to play out is that the Coulson we saw die was just a product of the Life Model Decoy, which would easily allow Iron Man 3 to introduce us to another character...